Alloys containing rare earth elements (R) have excellent magnetic properties and are used for permanent magnets. Especially advantageously used for permanent magnets are R-Fe-B alloys such as, for example, Nd-Fe-B. By using R-Fe-B alloys, permanent magnets having excellent characteristics are obtained by mechanically crushing and pulverizing an ingot of the alloy into a fine powder followed by compacting in a magnetic field, sintering and heat treating.
However, in the processing of R-Fe-B alloy powder into a permanent magnet material, the powder--especially when milled to a three-micron mean diameter size--is typically excessively reactive with air. Even when the final milling is carried out under hexane, this excessive reactivity causes the powder to burn when it comes into contact with air or oxygen-containing gas. Loss of large quantities of alloy powder by burning is commonplace in the magnet industry, especially during compaction, and prevents the attainment of high permanent magnetic quality. This burning phenomenon not only is economically disadvantageous due to loss of large quantities of alloy powder but also is a safety hazard. Accordingly, processing techniques which do not effectively counteract this phenomenon are disadvantageous.